The present invention relates to an indexable insert for copy turning with nose point angles less than 60.degree., which cutting insert has a rhombic basic form including an upper surface, and a bottom surface interconnected by side surfaces, wherein at least a part of the intersection lines between the side surfaces and the upper surface forms at least one main cutting edge, a secondary cutting edge and a curved corner cutting edge therebetween.
For copy turning nowadays, to a large extent, indexable inserts are used with nose point angles below 60.degree., wherein an ordinary value on the nose point angles is 55.degree., which enables application of the cutting inserts within a broad range. On the market nowadays a number of different types of indexable inserts with 55.degree. nose point angle are found, among which types rhomboidic, rhombic and regular triangular indexable inserts can be mentioned.
In copy turning the following properties regarding feature and economy are desirable:
1) Good chip control, i.e., favorable chip guidance and chip breaking. PA1 2) No movement of the cutting insert under impact of cutting forces. PA1 3) Possibility to engage at 30.degree. when inward copying is practiced.
When copy turning in certain materials or in slender work pieces and also in usage on unsteady machines and in internal metal working, low cutting forces and preferably a positive chip angle on the copying insert are desirable. Simultaneously there is a demand in modern machines that the copy turning insert to be used will be able to give the best possible surface finish of the machined surface. Sometimes surface finish can be improved by using higher cutting speed and neutral or positive rake angles. A certain sensitivity for the adjustment of the setting angle will however remain.
It is a purpose of the invention to achieve a new and improved indexable insert for copy turning to avoid or alleviate the problems of the prior art and which enables attainment of all the above indicated desirable properties at the same time as the feed can be increased considerably.